Horsley was born in Auckland, New Zealand, on 3 February 1871, to Laura née Young, a schoolteacher, and William Woodward, a farmer who had also been a teacher.
[1] When Horsley graduated alongside Constance Frost, Daisy Platts and Jane Kinder in 1900, only two women had previously gained medical degrees in New Zealand, Emily Siedeberg and Margaret Cruickshank.
She was known to sometimes ring home during administration of an anaesthetic to ask someone to turn the jam off, and her children recalled completing homework in the back of the car while she attended patients.
[2] From 1936–1946, she was an anaesthetist at the Mater Misericordiae Hospital, and worked privately for surgeons including Sir Carrick Robertson and James Hardie Neil.
[2] Horsley worked throughout the plague scare of 1900 and the 1918 influenza epidemic, and was a member of the medical relief team after the Hawke's Bay earthquake of 1931, in which hundreds were killed and thousands injured.